Magnetically operated reed switch



Jan. 20, 1970 G. A. HARRIS, JR 3,491,317

MAGNETICALLY OPERATED REED SWITCH Filed June 5, 1968 I 1 I m 1 1/ \l In 236 38 32 39 42 4 IINVENTOR 4:0,? ,4. A i/6W5 J,

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ATTORNEYS United States Patent 3,491,317 MAGNETICALLY OPERATED REED SWITCH George A. Harris, Jr., 110 Lincoln Ave., Saddlebrook, NJ. 07662 Filed June 5, 1968, Ser. No. 734,640 Int. Cl. H01h 51/28, 1/66 US. Cl. 335205 5 Claims ABSTRACT OF THE DISCLOSURE A switch operated by a permanent magnet within a hollow tube, resiliently biased toward one end of the tube and attached to a longitudinally slidable actuating member to be moved into and out of position with respect to a reed switch parallel to the tube to cause the reeds to move together when the magnet is in one position and apart when it is in an alternative position. A multiplicity of reeds may be grouped around a single magnet to be actuated thereby, and the reeds may also be placed with respect to the field of the magnet to be either normallyclosed by the field of the magnet when the actuating member is in its rest position or normally-open when the actuating member is in its rest position.

This invention relates to a magnetically operated reed switch and particularly to a miniature switch with one or more magnetic reed capsules located adjacent a slidable magnet.

The magnetic reed switch of the present invention uses reeds of magnetic material incapsulated in small glass tubes and having terminals extending from the ends of the tubes. There are several types of such reed switches.

One type has two relatively long reeds, one entering each end of the capsule with proximal ends of the reeds slightly overlapping and both free to move into contact with each other when suflicient magnetic flux is induced in them. Another type of reed switch has a relatively rigid reed at one end and a flexible reed at the other. Still another switch has two reeds entering the capsule from one end and one entering from the other end. The free end of the single reed is resiliently biased into contact with one of the two reeds, which is made of nonmagnetic material, and away from contact with the other of the two reeds. The latter is made of magnetic material so that suflicient flux linkage with the latter reed and the single reed at the other end will pull the single reed out of contact with the nonmagnetic reed and into contact with the magnetic one. Still other forms of reed capsules may be utilized in the present invention.

The present invention utilizes a hollow tube in which a magnet is slidably positioned and is attached to an actuating member that extends partly into and partly out of the tube. A spring within the tube resiliently biases the magnet toward one end, but the magnet and actuating member are prevented from moving beyond a certain point by a transverse member that engages a longitudinal slot in the tube. At each end of the tube is a non-conductive disc. Each of the discs has a plurality of aligned holes or openings with metal members framing or partially framing the openings to receive the terminals of the resilient capsules and to permit the terminals to be attached to the discs by being soldered or otherwise conductively joined to the metal that frames the openings. The metal members on one or both discs may be printed circuits. Alongside each reed capsule is a conductor, which may be a piece of straight wire that rests in another pair of aligned openings in the discs and is joined at one end by a section of the printed circuit to one terminal of the adjacent reed capsule. Terminals are provided in the discs at the other end of the tube to receive the other terminal of the reed capsules and the other end of the conductor.

The invention will be described in greater detail in the following specification together with the drawings in which:

FIG. 1 is a cross-sectional view of a reed switch constructed according to the invention; and

FIG. 2 is a plan view of a printed circuit disc as used in the switch of FIG. 1.

FIG. 3 shows a modified terminal lug useable with the reed switch of FIG. 1.

The switch in FIG. 1 comprises a magnet 11 permanently magnetized to have a north pole at one end and a south pole at the other and located within a hollow tube 12. One end of the magnet is attached to an actuating member 13 that extends partly into the tube 12 and partly out of it, and, the magnet and the actuating member may be glued together if desired. A spring 14 resiliently presses against one end of the magnet 11 and biases the magnet and the actuating member toward the left hand end of the tube 12 as viewed in the drawing. The spring butts up against a plug 16 that fills the other end of the tube 12 and is adhesively joined thereto. In order to prevent the magnet and the actuating member from being pushed entirely out of the tube 12, a transverse pin 17 is pressed into the actuating member 13. The pin 17 engages a longitudinal slot 18 shown in broken lines in the tube 12 to determine the limits of movement of the actuating member 13 and the magnet 11 in both directions.

At one end of the tube 12 is a disc 19 of insulating material which has a counterbored hole 21 into which the end of the tube 12 fits and a central passage 22 through which the actuating member 13 extends. The disc 19 has a plurality of holes 23 bored at least into one surface thereof, if not entirely through the disc, and a conductive circuit 24 printed on that surface. At the other end of the tube 12 is a second disc 26 that has a recess 27 in one surface into which one end of the tube 12 fits. The disc 26 also has openings 28 bored through it with terminal lugs 29 affixed therein. The openings 28 are aligned with the openings 24 in the disc 19.

Between the discs 19 and 26 and parallel to the tube 12 are two magnetic reed switch capsules 31 and 32. The capsule 31 contains two magnetic reed members 33 and 34 that either extend through the ends of the capsule to form terminals 36 and 37 or are attached to terminals that extend through the ends. The terminal 36 is fitted into the opening 23a in the disc 19 and is soldered to the printed circuit 24a. The other terminal 37 extends into a recess in the lug 29a and is soldered thereto. The

capsule 32 has magnetic contacts 38 and 39 with respective terminals 41 and 42. The terminal 41 extends into the openings 23b and is soldered permanently to the printed circuit 24b, while the other terminal 42 extends into a recess in the lug 29b and is soldered thereto.

As may be seen, the overlapping ends of the contacts 33 and 34 are in different longitudinal planes than the over-lapping ends of the contacts 38 and 39. These different planes correspond to different operating characteristics of the capsules 31 and 32. The contacts 38 and 39 are resiliently biased apart but are normally held together by flux from the magnet 11 when the magnet is in the position shown. The contacts 33 and 34 are also resiliently biased apart but are not magnetically brought together until the actuating member 13 is depressed to drive the magnet 11 longitudinally along the tube 12 to the alternative limit position permitted by the interengagement between the pin 17 and the slot 18. At the same time such movement of the magnet 11 reduces the flux linking the contacts 38 and 39 and permits them to spring apart.

Thus the capsule 31 contains, in effect, a pair of norma lyopen contacts while the capsule 32 contains a pair of normally-closed contacts for the switch.

The entire switch is enclosed in a metal container 43 having a threaded bushing 44 at one end to be mounted on a panel and through which the actuating member 13 extends. The main part of the container 43 is a cylinder that encloses and shields the capsules 31 and 32 as well as the discs 19 and 26, and the end of the container is mechanically joined to the disc 26 by detent depressions 46 and 47 pressed therein.

In order to make connection with the terminals 36 and 41 on the interior of the container 43, a fixed conductor is included to extend from the disc 19 to the disc 26. One such conductor is required for each of the capsules in the switch. FIG. 2 shows a plan view of the disc 19 with four printed circuits 24a-24d thereon. Also shown are cross-sections of the terminals 36 and 41 along with cross-sections of wire conductors 48 and 49 which are soldered to the printed circuits 24a and 25b to be held within openings in the disc 19. The wires 48 and 49 extend longitudinally through the container 43 along with the capsules 31 and 32 and fit in additional terminal lugs (not shown) inserted in the disc 26 in alignment with the holes 230 and 23d in the disc 19. There is sufiicient room in the container 43 for capsules similar to the capsules 31 and 32 and four wire connectors parallel thereto.

FIG. 3 shows a modified terminal lug 51 inserted in the disc 26. The terminal lug 51 has a hollow metal tubular portion 52 that extends beyond the disc to receive the terminal 37 of the reed capsule 31 and to permit the terminal 37 to be joined to the terminal lug 51 by a mechanical crimping process instead of having to be soldered.

Some magnetic reeds are adversely affected by the heat required to solder their terminals, and it is necessary in such cases to provide a heat sink or to take other precau tions to avoid damaging them. If the whole switch is to be made as short as possible, there may not be room enough for a heat sink, which is basically a comparatively massive piece of metal, to be placed in contact with the terminal 37 between the capsule 31 and the point of attachment to the lug 29a shown in FIG. 1. The crimping operation requires less space, is safer, can be mechanized, and is therefore capable of turning out more uniformly excellent products. Substantially balanced pressure is applied to opposite sides of the metal tube 52 in the direction of the arrows. This produces good mechanical and electrical connection between the tube 52 and the terminal 37 without putting any substantially bending pressure on the terminal 37 at the point where it passes through and ishermetically sealed to the glass wall of the capsule 31. As a further aid in preventing any breaking stress from being applied to the capsule 31, the terminal 36 at its other end is not secured to the'disc 19, or the printed circuit 24a (shown in FIG. 1) until after the terminal 37 has been crimped.

What is claimed is:

1. A switch comprising: a hollow tube; a magnet slidably held within said tube; a spring within said tube between said magnet and one end of said tube; an actuating member partly within said tube at the other end thereof and partly extending out of said other end; a longitudinal slot in said tube near said other end; a transverse member aflixed to the portion of said actuating member within said tube, said transverse member extending through said slot to limit the movement of said actuating member; first and second insulating discs attached to said one end and said other end, respectively, of said tube; first and second substantially longitudinally aligned openings in said first and second discs, respectively; a conductor extending between and held within said openings; third and fourth substantially aligned openings in said first and second discs, respectively; a magnetic reed switch extending between and held within said third and fourth openings; a printed circuit on said first disc joining said first and third openings, one end of said conductor and one end of said switch being soldered to said printed circuit.

2. The switch of claim 1 comprising, in addition: a first connector terminal attached to said second disc and having a receptacle comprising said second opening; and a second connector terminal attached to said second disc and having a receptacle comprising said fourth opening.

3. The switch of claim 1 in which: said first disc has a central aperture and said actuating member extends through said aperture and said second disc has a counterbored recess in one surface and said one end of said tube fits in said recess.

4. The switch of claim 1 in which: said magnetic reed switch comprises a pair of magnetic contact members resiliently biased apart and magnetically moved together only when linked by sufficient magnetic flux, said magnet being positioned within said tube and normally resiliently biased by said spring longitudinally away from a position in which sufficient flux from said magnet is linked with said magnetic contact members to move said members together, said longitudinal slot being long enough to permit said magnet to move to an alternative position in which sufiicient flux from said magnet links said contact members to move said contact members together.

5. The switch of claim 1 in which: said magnetic reed switch comprises a pair of magnetic contact members resiliently biased apart and magnetically moved together only when linked by sufi'icient magnetic flux, said magnet being positioned within said tube and normally resiliently biased by said spring longitudinally into a position in which suflicient fiux from said magnet is linked with said magnetic contact members to move said members together, said longitudinal slot being long enough to permit said magnet to move to an alternative position in which insufficient flux from said magnet links said contact members to move said contact members together.

References Cited UNITED STATES PATENTS 3,271,708 9/1966 McCormick 335205 OTHER REFERENCES IBM Technical Disclosure Bulletin: Multiconfiguration Pressure Switch; Bolan, et al.: vol. 8, No. 7, December 1965.

BERNARD A. GILHEANY, Primary Examiner R. N. ENVALL, JR., Assistant Examiner U.S. Cl. X.R. 335206 

